Scientific Forecaster Discussion
fxus61 klwx 150211
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1011 PM EDT Sat Sep 14 2019
a cold front will slowly pass through the area overnight into
early Sunday. High pressure will follow for much of next week
as what is currently Tropical Storm Humberto meanders off the
coast of the southeastern United States.
Near term /until 6 am Sunday morning/...
a weak cold front will continue to slowly pass through the area
overnight from northwest to southeast. An isolated shower is
possible along the boundary, but much of the time should be dry.
This is because the boundary is moving into a slightly more
stable area (cloud cover kept instability down east of the Blue
Ridge mountains) and it is moving through at an unfavorable
time. Also, the lift along the boundary is weak.
Low clouds east of the Blue Ridge should scour out toward
morning as drier air works its way in from the northwest.
However, the flow will be light and radiational cooling will
allow for some fog. The best chance for fog will be in the river
valleys, sheltered valleys and rural areas west of the Blue
Ridge mountains where the atmosphere is most likely to decouple.
Locally dense fog is possible across these areas. Min temps will
range from the 50s in the cooler valleys to the 60s for most
Short term /6 am Sunday morning through Monday night/...
rain from the evening prior could lead to some patchy fog in
places normally prone to it. Otherwise, a much drier day
expected on Sunday, as high pressure builds into the region
behind the cold frontal passage. The only exception could be
areas in southern MD, where the front may not quite be gone
tomorrow morning, so some lingering showers are possible, and
maybe even a rumble of thunder. Tomorrow will certainly be
warmer, with highs into the mid 80s, as a ridge begins to build
into the region, resulting in mid-level height rises. Cooler
temps expected Sunday night, with lows in the low 60s.
The aforementioned upper ridge will continue to build and
strengthen over the region on Monday. This will likely be the
hottest day of the week, with highs into the upper 80s or so.
However, with winds out of the northwest, humidity will not be
of much concern, as dew points will only be in the low 60s. With
limited moisture, expect only some cumulus, despite the heat.
Mostly dry conditions on Monday night, though some guidance is
hinting at a frontal passage out of the north Monday night,
which could bring some showers to the region. Keeping chances
low at this point, given the lack of moisture available.
Long term /Tuesday through Saturday/...
on Tuesday, the cold front is expected to be well south of the area
as high pressure across the Great Lakes slides east and builds south
across the mid-Atlantic region and remains for the remainder of the
work week. Dry weather is expected through the long term period
although with northeasterly low level flow, there will be some
cloudiness that times east of the Blue Ridge.
Aviation /02z Sunday through Thursday/...
cigs around 3kft are expected east of the Blue Ridge, but
slightly drier air should cause clouds to scour out between
04-08z overnight. Patchy radiational fog may reduce vsbys toward
morning, especially over the western terminals. Skies will
clear completely for tomorrow, with VFR conditions expected once
any radiational fog Burns off.
High pressure is expected to cover the region Tuesday and Wednesday.
Behind the cold front Tuesday morning...a period of MVFR ceilings is
possible for iad/dca...but expecting VFR for the remainder of the
winds may approach Small Craft Advisory criteria ahead of a cold front late this
evening into the overnight hours from the south. An Small Craft Advisory has not
been issued since the gradient is relatively weak.
With high pressure building into the region, not expecting
winds to approach Small Craft Advisory criteria Sunday through Monday night, so
not expecting any marine hazards.
Winds are expected remain below Small Craft Advisory levels through the extended.
Near Small Craft Advisory level wind gusts are possible Tuesday morning due to
northerly channeling behind the front.
tidal anomalies should decrease enough overnight, allowing for
water levels to remain below minor flooding thresholds during
the next high tide cycle overnight into Sunday.
District of Columbia...none.